The following relates to the spectroscopy arts, Raman spectroscopy arts, particulate detection or sampling arts, optical characterization arts, and so forth.
WO 2007/009119 A2 published Jan. 18, 2007 is incorporated herein by reference in its entirety. WO 2007/009119 A2 relates to systems and methods for biological and chemical detection and names Battelle Memorial Institute, Columbus, Ohio, USA as applicant.
Raman spectroscopy is known for use in microbiological testing. By way of illustrative example, some such techniques are disclosed in WO 2007/009119 A2, and a known microbiological testing system employing Raman spectroscopy is the Rapid Enumerated Bioidentification System (REBS) developed by Battelle Memorial Laboratories (Columbus, Ohio, USA).
In some types of microscopy, line illumination is employed. Such illumination advantageously provides high resolution controlled by the “width” or narrow dimension of the line illumination, and parallel sampling along the “length” or long dimension of the line. For some cell detection or sampling (e.g., counting) applications, the width of the line illumination is preferably about one micron, which corresponds to a typical size of prokaryotic cells (bacteria, by way of illustrative example) of interest in medical, biohazard, or other applications.
Typical light sources for illuminating the microscope field of view include arc lamps and semiconductor lasers. Such light sources are commercially available, but are generally designed to produce circular illumination. In the case of edge emitting diode lasers, which naturally produce a high aspect ratio beam, the commercial product is typically packaged with micro-optical components (a micro-cylindrical lens, by way of illustrative example) to circularize the beam output. The circular beam is converted to line illumination of the desired aspect ratio using an aspherical lens, cylindrical lens, or the like.
In the context of sampling microarrays, it has also been suggested to produce line illumination by focusing the high aspect ratio beam of an edge emitting diode laser. See WO 2008/0117518 A1. However, an edge emitting laser actually generates a strongly diverging beam with a high degree of astigmatism. In commercially available edge emitting laser packages, a microlens or other near-field optic is typically provided to circularize the output beam. Moreover, Raman spectroscopy and some other spectroscopy techniques require a highly monochromatic light source. For example, in the case of Raman a spectral full width at half maximum (FWHM) of order 0.1 nanometers or smaller is desired. An edge emitting laser produces a beam with a large spectral FWHM, for example, of order 3 nanometers in the case of some commercially available edge emitting lasers.